What Can Coolant Analysis Uncover?

Coolant analysis is essential to successfully managing fleet maintenance and is instrumental in identifying cooling system issues and deficiencies in maintenance practices. Coolants transfer heat from fluids and components and provide metal corrosion and cavitation protection while maintaining a stable state of alkalinity within the cooling system. If a coolant isn’t doing its job by effectively removing heat generated from the combustion of fuel in the engine block, premature system failure can occur.

Proper routine coolant analysis can identify cooling system problems before they wreak havoc on other systems and components. Testing regularly can help fleet managers significantly reduce major repairs, increase equipment uptime, maintain high productivity levels and ensure operational safety.

Silicon, Boron, Molybdenum and Phosphorous

Silicon, boron, molybdenum and phosphorous are inorganic “inhibitors.” They are used in various coolant formulations to maximize engine metal protection and control pH. The amount present is dependent upon the coolant’s formulation.

Calcium and Magnesium

These naturally occurring minerals are often found when poor tap water is used for “topping off,” or replenishing coolant levels. As contaminants, they prevent inhibitors from working effectively. When they react with silicate, sulfate or the formation of carbonate, scale can form on hot metal surfaces. Scale formation insulates these surfaces causing localized engine overheating or hot spots which can result in cracked heads, head gasket failure, clogged radiators and oil coolers as well as burnt valves and oil oxidation.

When test results reveal high levels of either calcium and/or magnesium, the laboratory will recommend correcting the source water or source of hardness contamination, cleaning the system with a cleaner designed to remove heavy metal and scale and flushing thoroughly before refilling with new coolant.


Corrosion indicates that buffers are no longer efficient at countering the formation of acid that results from thermal degradation. Typical sources of corrosion include:

  • Iron from the liner, water pump or the cylinder block/head
  • Aluminum from radiator tanks, coolant elbows, piping, spacer plates or thermostat housings
  • Copper or lead from the radiator, oil cooler, aftercooler or heater core


Nitrite is present in nitrite OAT (NOAT – Nitrite Organic Acid Technology), hybrid (HOAT – Hybrid Organic Acid Technology) or heavy duty and fully formulated conventional coolants. Some of these coolants contain a combination of both nitrite and molybdenum. Knowing whether an engine’s coolant exceeds the maximum acceptable level of nitrite or nitrite and molybdenum (combined these should be no more than 3200 parts per million) helps prevent inhibitor fallout which can lead to cavitation and glycol degradation.

Organic Acid

Organic acids function as the main inhibitor package in extended life coolants. Diluting these inhibitors more than 25% by mixing coolant formulations or topping off with water can leave the system vulnerable to corrosion. Coolant analysis is imperative to monitoring proper engine protection when using extended life coolant formulations.


Although water is an effective fluid for heat transfer, its effectiveness is limited to a specific range of temperatures. The addition of glycol in a coolant offers a wider operating range than that of either glycol or water alone. Ethylene glycol is the most commonly used due to its high functionality and low cost.

Glycol levels indicate a coolant’s ability to properly maintain freeze point and boil point protection. An adequate glycol range should be between 45% and 60%. Levels of glycol higher than this can lead to heat transfer issues, cause additive dropout and decrease the life of the coolant.


pH is a measure of the coolant’s acidity or alkalinity and can provide clues to possible internal chemical reactions taking place that could lead to premature failure. Without proper pH levels, the coolant’s ability to inhibit corrosion is diminished. An adequate pH range for conventional coolants is 8.0-11.0, and 7.0-9.5 for organic acid extended life coolants.

Professional coolant analysis includes maintenance recommendations that can help fleet managers take the guesswork out of results. As engine designs evolve over time, cooling systems face even greater challenges in protecting these complex systems from contamination and corrosion. Adopting coolant analysis into routine fleet maintenance reduces fleet downtime, eliminates unnecessary coolant drains, lowers the costs of coolant replacement and disposal and decreases the frequency of engine and system repairs.

The Coolant Changeover Process

When a coolant is no longer suitable for use due to either natural breakdown or the introduction of outside contaminants, the system should be drained, flushed with water and replenished with new coolant. Cleaners should only be used if there is oil, sludge, heavy metal or scale present.

Because coolant systems are such a vital part of system maintenance, it’s important to establish routine intervals for coolant analysis to identify small issues, such as air leaks, glycol degradation, inhibitor depletion or coolant maintenance deficiencies that can become larger issues later such as corrosion, cavitation, localized overheating or electrolysis.

Improperly maintained systems can shorten equipment life and often result in equipment failure. Incorporating routine analysis into preventive maintenance schedules allows fleet managers to closely monitor cooling system health and prevent unnecessary equipment breakdown, losses in productivity and unnecessary labor and repair costs.